Deleted = gone!
Either you get the necessary info from a backup or you can go from memory and redefine the group ad readd the members and the permissions.
Do that through the ACP and DO NOT start adding and editing in the database unless you really know what you are doing (probably not or you wouldn't request support).
This might seem a daunting task but the data has been deleted from the database so there not much choice.

As above - but I would go for the database restore option as it will be quicker and easier

DavidRemember: You only know what you know and - you don't know what you don't know!My CDB Contributions | How to install an extensionI will not be accepting translations for any of my extensions in Github - please post any translations in the appropriate topic.No support requests via PM or email as they will be ignored